1. Field of the Invention
The present invention relates to cyclonic separation apparatus and particularly, but not exclusively, to cyclonic separation apparatus for use in vacuum cleaners.
2. Related Background Art
High separation efficiency cyclonic separation is generally achieved by connecting several separation stages in series. The successive stages are typically arranged in increasing efficiency in the direction of gas flow, although it is known to provide adjacent stages of similar efficiency. For example, GB2424603 discloses a three-stage separator comprising a low-efficiency cylindrical cyclone as the first stage, an annular array of parallel-connected high-efficiency cyclones located in a chamber above the first stage and a second similar array of high-efficiency cyclones as the third stage located in a chamber above the second stage.
The height of this arrangement renders it of limited use to vacuum cleaners, where compact dimensions are required. In addition, the respective separation stages discharge their separated material into three separate collection chambers located below the respective cyclone outlets. The collection chambers must be emptied individually, which can be a time consuming process since several parts are required to be removed from the separator unit.
GB2424606 discloses a multi-stage cyclonic separator for a vacuum cleaner whereby the high efficiency mini-cyclones of the second and third stages are arranged around the periphery of the of the low-efficiency first stage cyclone. However, the peripheral arrangement of the higher-efficiency stages is restrictive of the number of cyclones possible in the individual stages, having regard to the dimensional limitations applicable to vacuum cleaners.
U.S. Pat. No. 2,372,514 discloses three vertically stacked separation stages, but incorporates a separated material collection arrangement whereby material falling from the cyclone outlets is collected in funnels and ducted to a single outlet at the base of the separation unit. The second separation stage of this separator comprises an annular array of eight conical cyclones surrounding a central core tube, and the third stage comprises twenty-four small cyclones arranged in a cluster.
Accordingly, there is a requirement for a cyclonic separation apparatus which provides the separation efficiency offered by multi-stage, series connected cyclone separators but which is sufficiently compact to enable the apparatus to be utilised in a vacuum cleaner.